Vodacom/Samsung shocking repair service

I have a Samsung S4 mini on a Vodacom contract. During November 2014 I started having problems. At first it switched off by itself and eventually just didn't switch on, neither did it charge or switch on or charge when plugged into the charger. This seems to be a common problem with Samsung devices. One of my employees have the same phone and experienced exactly the same problem. I returned the phone to my nearest Vodashop, where they sent it to the Samsung repair center in Bloemfontein. After a week or so they returned the phone with the only explanation that it was some hardware error. No other details. About two months later, mid Feb, I had exactly the same problem. Once again I took the phone to the Vodashop where they sent it off to the repair center again. I received a call from the repair center and was given a quote for the repair of the phone. I asked the person why I should pay for the repair of the same issue I had previously. I was told that she would speak to her manager and get back to me. 4 days later and I still haven't heard from the repair center, except for a sms saying that the qoute for repair was rejected and that they are sending me the phone, not repaired.